Process of degreening and ripening fruit



July 28, 1970 J. A. ANDERSEN ET 3,522,057

PROCESS OF DEGREENING AND RIPENING FRUIT 2 Sheets-Sheet 1 Original FiledDec. 20, 1966 AA M MAAMMAAMUF mw s m N am mRA EEM VD: mm 6 L 2 L E NS m1| wR 1 5 22 Y. w IL B w I ||H/||||1.. .1 I F m. ow 9 TORNE Y July 28,1970 J. A. ANDERSEN ET AL 3,522,057

PROCESS OF DEGREENING AND RIPENING FRUIT Original Filed Dec. 20. 1966 2Sheets-Sheet 2 [I T gfi o 2 m 3 515-5 '83 n 1% m 1 u g e m 82) ilkINVENTORS JOHN A. ANDERSEN RUSSELL M. MAGNER United States Patent Office3,522,057 Patented July 28, 1970 3,522,057 PROCESS OF DEGREENING ANDRIPENING FRUIT John A. Andersen, Los Altos, and Russell M. Magner,

Atherton, Calif., assignors to General Industrial Equipmerit Company,Palo Alto, Calif., a corporation of California Original application Oct.20, 1966, Ser. No. 588,221. Divided and this application Jan. 16, 1968,Ser. No. 719,806

Int. Cl. A231 1/00 US. Cl. 99103 4 Claims ABSTRACT OF THE DISCLOSUREProcess of degreening and ripening fruit by treating stored fruit with acirculating air stream maintained at a selected fruit processingtemperature. The dew point temperature of the air stream is maintainedas closely as possible to the temperature of the coldest portion of thefruit until reaching a selected dew point temperature which isthereafter maintained until the fruit is degreened and ripened.

This application is a division of our copending application Ser. No.588,221, now Pat. No. 3,388,863, filed on Oct. 20, 1966, which in turnis a continuation of application Ser. No. 366,518, filed May 11, 1964,now abandoned.

This invention relates to the humidity and temperature control of anenclosed space and more particularly to means and a method formaintaining a constant relative humidity within a confined space at aselected temperature, and further for increasing and decreasing theabsolute humidity with increasing and decreasing temperaturerespectively.

Constant relative humidity chambers find extensive application inindustry. For example, in the fruit industry it is common practice toremove fruit from trees before it has obtained the desired color ordegree of ripeness and, thereafter, degreen or ripen the fruit indegreening or ripening rooms. This degreening or ripening processusually requires raising the temperature of the fruit after placementinto an enclosed space such as a degreening or ripening room toapproximately 72 F. This temperature is usually maintained until thefruit has achieved the desired color or degree of ripeness. Thereafterthe temperature of the room is lowered to the ambient or out: sidetemperature so that the fruit may be removed for further processing suchas packing and shipping.

For the proper processing of the fruit, and particularly for the fruitto maintain its appearance, the relative humidity in the processing roomshould be maintained as constant as possible, particularly at theselected processing temperature. It has been found that for certainfruits a relative humidity of about 88% at a processing temperature ofabout 72 F. is desirable. Since the relative humidity is the ratio ofthe partial water vapor pressure to the vapor pressure at the processingroom temperature, the relative humidity for a given amount of Water inthe processing room air changes with temperature. Accordingly, duringthe heating cycle water must constantly be added to the air if therelative humidity is to be prevented from decreasing to too low a value.Conversely, dry air must constantly be added when the temperature in theprocessing room is decreased to prevent the relative humidity fromexceeding too high a value.

If, during the process of fruit degreening or ripening, the relativehumidity falls below an optimum value for any appreciable length oftime, the fruit tends to dry which deleteriously afiects its marketvalue as well as its weight. If the relative humidity is higher than anoptimum value for any appreciable length of time, the fruit has atendency to foul which can result in a severe loss. Accordingly, theprocess of degreening or ripening the fruit after it has been picked ina green or unripe state, as the case may be, requires that the humiditybe maintained substantially constant at the processing temperature, andthat water be respectively added and removed during the raising andlowering of the temperature to and from the processing temperature.

Heretofore a number of attempts have been made to inexpensively andeconomically maintain the relative humidity of the processing room at aselected optimum value but none, to our knowledge, have succeeded in doing so during the period of processing the fruit and further of changingthe absolute humidity during the raising and lowering of the temperaturein the direction towards maintaining the relative humidity substantiallyconstant.

It is therefore a primary object of this invention to provide anapparatus for installation into a processing room which is capable ofmaintaining the relative humidity of the processing room constant.

It is another object of this invention to provide a means and a methodfor maintaining the humidity of the air within an enclosed space at aselected dew point temperature.

It is a further object of this invention to provide an enclosed spaceincluding means to inexpensively and reliably control the temperatureand relative humidity therein independently of one another.

It is a further object of this invention to provide an air-conditioningdevice capable of controlling both the relative humidity and thetemperature within an enclosed space.

It is a further objective of this invention to provide a method forcontrolling the relative humidity and the temperature within an enclosedspace.

It is a further object of this invention to provide an apparatus and amethod for maintaining the humidity of an air mass at a selected dewpoint temperature within an enclosed space maintained at a selectedtemperature.

It is another objective of this invention to provide an apparatus and amethod for controlling the relative humidity within an enclosed spaceinexpensively and reliably by utilizing substantially Wet or saturatedair generated in the space to increase the humidity and substantiallydry or unsaturated air from outside the space to decrease the humidity.

' It is also an objective of this invention to provide a means andmethod for adding water to the air in an enclosed space during theraising of the space temperature and for adding dry air to the spacewhen dropping the temperature to maintain the absolute humidity changesin the same direction as the temperature changes.

In accordance with a preferred embodiment of this invention, anapparatus is provided which continuously saturates an air stream passingtherethrough adiabatically by adding water to provide a saturated airstream. The temperature of the saturated air stream is sensed with afirst conventional dry bulb thermometer providing the dew pointtemperature. The saturated air stream is then passed through a heaterwhich is controlled by a second conventional dry bulb thermometerlocated to sense the dry bulb temperature of the fruit in the spacewhose humidity and temperature is to be controlled.

The first and second thermometer are respectively connected to a firstand second thermostat which provides a first and second temperaturesignal commensurate with the sensed temperature. The second temperaturesignal is utilized to control the temperature of the heater throughwhich the saturated air flows to supply heat when the fruit in thechamber is below the desired chamber temperature and to inactivate theheater when the fruit in the chamber has reached or exceeded the desiredchamber temperature. In this manner the chamber temperature iscontrolled.

The relative humidity is controlled by developing a control signal whenthe first temperature signal is greater than a selected dew pointtemperature. The control signal is utilized to operate a dampermechanism which changes the inflow port of the apparatus fromcommunication with the enclosed space from which it receives wet air tocommunication with the outside from which it receives dry air. In analternate embodiment, the control signal may be developed by comparingthe first and second temperature signals and developing a dilferencesignal which according to the psychrometric chart reflects the desireddew point temperature at the selected space temperature.

Even though this invention is being described with particular emphasison the degreening of citrus fruits, it is to be understood that it isequally applicable to the ripening of other fruit and to many otherprocesses which require control of temperature and humidity. Forexample, the apparatus and method of this invention is ideally suitedfor controlling the temperature and humidity of greenhouses for thegrowing of tropical plants, or for controlling of terrariums in whichtropical animals are kept.

Further objects and advantages of the present invention will becomeapparent to those skilled in the art to which the invention pertains asthe ensuing description proceeds.

The features of novelty that are considered characteristic of thisinvention are set forth with particularity in the appended claims. Theorganization and method of operation of the invention itself will bestbe understood from the following description when read in connectionwith the accompanying drawing in which:

FIG. 1 is a side view, partially in section, of the airconditioningdevice'of this invention;

FIG. 2 is a front view, partially in section, of the device shown inFIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a partial side view of a processing or degreening room havingthe device of this invention installed along an end wall;

FIG. 5 is a partial top view taken along line 55 of FIG. 4; and

FIG. 6 is a schematic block diagram of the control system of the deviceshown in FIG. 1.

Referring now to the drawings there is shown an exemplary embodiment ofan air-conditioning device constructed in accordance with this inventionand generally designated by reference character 10. Air-conditioningdevice 10 has an uprightly disposed, tubular enclosure 12 which may beof rectangular cross section as indicated, or which may take any otherdesired shape. Basically, enclosure 12 forms a vertical flow channelwhich is open at the top for discharge and which is seated upon asuitable foundation 14.

Enclosure 12 is provided with a pair of diametrically opposed inputports diagrammatically indicated by arrows 16 and 18 respectively and anoutput port similarly indicated at 20. Input port 16 has associatedtherewith an input control means 22 and input port 18 has associatedtherewith an input control means 24. Input control means 22 and 24preferably take the form of adjustable dampers which are moveablebetween a closed and open position across the associated input ports tocontrol the effective input port opening as will be explained. A commonactuation means 26 is connected to damper 22 through linkage 28 and todamper 24 through linkage 30 to oper ate dampers 22 and 24 in adifferential manner. In other words, actuation means 26 is connected tothe dampers in such a manner that the change of one damper from itsclosed to its open position produces an opposite change in the otherdamper. Lead 101 provides the control signal.

Output port formed by the open upper end of enclosure 12 is providedwith an air circulatingmeans 34 which may take the form of a pair ofrotating fans 35 and 36 which draw air upwards and force the air outthrough output port 20. To establish an eflicient flow channel utilizingfans 35 and 36 it has been found useful to seal off output port 20 bymeans of a closure plate 38 which includes a pair of fan openings 39 and40 dimensioned for accommodating the fan blade of fans 35 and 36respectively. In this manner an eflicient circulating means is providedwhich creates an upwardly flowing air stream in enclosure 12 forcing theadmission of air through input port 16 or 18 or both.

Mounted inside enclosure 12 and immediately below circulation means 34is a heating means 42 whose function is to impart heat to the airpassing therethrough. Heating means 42 may comprise a water or steamjacket in the form of a coil to which steeam from an input pipe 43 isadmitted to heat the same. The steam, after heating, is returned to asteam supply through output pipe 44. Instead of utilizing steam toactuate heating means 42, an electrical heating coil may be used inwhich case pipes 43 and 44 are replaced by wires carrying the electricalcurrent. Heating means 42 is provided with a heating control means whichmay take the form of an electrically controlled flow valve 45 in inputpipe 43 having a valve control element 46 for controlling the steam flowtherethrough in accordance with the amount of heat to be imparted to theair stream flowing through enclosure 12 as will be explainedhereinafter. Lead 100 provides the control signal.

Also mounted inside enclosure 12 and above input ports 16 and 18 is anair stream saturation means generally designated by reference character50 for adiabatically saturating the air stream with water. Saturationmeans 50 comprises a spray tree 52 including one or more spray pipes 53each having many closely spaced, downwardly expelling openings ornozzles 54 through which water is discharged in a fine spray to saturatethe upward flowing air.

Water is supplied to spray pipes 53 by means of a supply pipe 56connected to the upstream end of a spray pump 58. The downstream end ofthe spray pump 58 is connected through a pipe 60 to a reservoir at thebottom of enclosure 12. In this manner a water circulating system isformed.

A water inlet, which also functions as an overflow outlet, is providedby a pipe 62. After the introduction of water into the bottom ofenclosure 12 through pipe 62 the same is circulated under pressure fromthe pump 58 to spray tree 52 for discharge through nozzles 54 tosaturate the upward flowing air.

Above spray tree 52 there is mounted, within enclosure 12, anelimination means 64 which has a large plurality of overlappingdeflectors 65 which operate upon the upwardly moving stream of saturatedair and eliminate or remove water droplets from the stream. In thismanner the upward flowing air stream is fully saturated corresponding toa relative humidity of substantially equal to 100% and carries nounabsorbed water droplets.

Positioned between elimination means 64 and heating means 42 is atemperature sensing means which may take the form of a conventionalgas-filled dry bulb tube. Thermometer 70 is connected, through a tube71, to a suitable potentiometer type thermostat 99 as will be explainedhereinafter in connection with FIG. 6. The function of sensing means 70is to provide an indication of the temperature of the saturated airstream prior to it being heated by heater means 42.

By Way of summary, enclosure 12 has a pair of differentially operatedinput ports 16 and 18 at its bottom just above a water reservoir throughwhich air is admitted into enclosure 12. The admitted air is forcedupwards through suction fans 35 and 36 and is expelled at the topthrough output port 20. As the air stream travels upwards through theenclosure, it is first saturated with water and unabsorbed waterdroplets are expelled. Thereafter, the temperature of the saturated airstream is determined and the saturated air is passed through the heaterfor subsequent discharge from the enclosure.

Referring now particularly to FIGS. 4 and 5, there is shown a typicalprocessing room 80 in which the airconditioning device of FIG. 1 isinstalled for maintaining a constant selected humidity while the fruitin the room is first brought up to and then maintained at a selectedprocessing temperature. A typical processing room for degreening orangesmay be 70 feet long, feet wide and 18 feet high and may requiretypically a circulation of 30,000 cubic feet of air per minute.Processing room 80 has a pair of side walls 81 and 82, a ceiling 83 anda floor 84. Further, processing room 80 has a pair of end walls 85 onlyone of which is shown and a partition wall 86 extending parallel to endwall 85 and suspended from ceiling 83 to define a space 88 into whichair-conditioning device 10 is placed. Partition wall 86 extendsdownwardly and terminates in edge 87 at a height above floor 84 which issomewhat above the opening of damper means 22. The space between edge 87and floor 84 defines a communication channel between the main portion ofprocessing room 80 and space 88 accommodating air-conditioning device10.

The upper portion of partition 86 is provided with a plurality of fans90 which push air at a desired flow rate from partitioned portion 88into the main portion of the processing room. The air return is providedby the communication channel 95 formed between the floor 84 and loweredge 87 of partition wall 86.

End wall 85 has an opening 92 dimensioned and positioned to be inregistry with damper means 24 which overlies input port 18 ofair-conditioning device 10. In this manner input port 18 is in directcommunication with the outside air. Input port 16, as best seen in FIG.4, is directly opposite partition channel 95. Accordingly, when dampermeans 22 is fully open (so that damper means 24 is fully closed) the airintake is entirely from the processing room. Conversely, when dampermeans 24 is fully open the air intake is entirely from the outside.

As a practical matter it has been found that air-conditioning device 10for degreening oranges only requires a capacity of about one-third orone-fourth of the desired fiow rate across partition wall 86 so that fora flow rate of 30,000 cubic feet per minute across wall 86 anair-conditioning capacity of about 10,000 cubic feet per minute is quitesufficient. In this manner about one-third of the air continuouslycirculated through the processing room is controlled by air-conditioningdevice 10. Of course, for other applications, more or less airprocessing may be required.

There is also provided an exhaust damper 97 which may conveniently beincorporated in end wall 85 to maintain the pressure in processing room80' at atmospheric pressure. When fresh air is taken into the room 80through input port 18, the excess air is bled through exhaust damper 97.A pair of doors, one at each end of the partitioned portion, allowsready access.

A further temperature sensing means such as a gasfilled dry bulbthermometer 96 is located in opening 95 and connected to a thermostat 98through a connection 94 which is conveniently located. Thermostat 98provides a temperature signal commensurate with the temperature of theair circulated through room 80 and more particularly of the air passingthrough opening 95.

Referring now to FIG. 6- there is shown, in schematic form, the meansutilized for controlling both the temperature and the humidity of theair being circulated through room 80. As previously explained,thermostat 98 provides a temperature signal on lead 100 commensuratewith the temperature of the air returned to the partitioned portionthrough opening 95. which is at the temperature of the stored fruit.This temperature signal is applied to valve control means 46 and opensthe same when the air return temperature is below a selectedtemperature. Once the stored fruit has reached or exceeds a selectedtemperature, valve control means 46 shuts off and heater means 42 isinactivated.

Thermostat 99 similarly provides a temperature signal on lead 101commensurate with the temperature of the wet air mass drawn throughdevice 10 prior to entering heating means 42 and subsequent to beingsaturated to a relative humidity of close to 100%. Thermostat 99controls damper control means 26 and may be directly connected theretoand set to a desired temperature so that when that temperature isreached or exceeded it moves the dampers to let in colder air which ismuch drier.

Instead of setting each thermostat to provide an output only when itsassociated thermometer reaches a selected temperature, i.e. essentiallyoperating in a digital fashion, the thermostats may be utilized in ananalog fashion. If so used, both temperature signals are applied to adifference detecting meter 102 (through lead 101 and 103) which is setto provide a damper control signal only when the difference isindicative to a selected temperature difierence, say 2 F. Thisconnection is. shown in dotted lines. Meter 102 may take the form of aconventional differential amplifier.

In operation, citrus fruit is placed into the main portion of theprocessing room when the same is at a low temperature, say 35 F. At thetime the processing room is loaded, it is in communication with theatmosphere so that its relative humidity is far below the desired valueof about 88%. The processing room is then sealed olf and thermostat 98is set to the desired processing temperature which is typically 72 F. Atthe same time thermostat 99 is set to a temperature which corresponds tothe necessary dew point temperature which provides the selected relativehumidity at the processing room temperature. For example, if the desiredprocessing relative humidity is 88% at the desired processing roomtemperature of 72 F., the dew point temperature, as determined frompsychrometric charts, is about 69 F. AC- cordingly, thermostat 99 is setto 69 F.

The term set as applied to thermostat 98 and 99 is used herein to denotethat the temperature signal initiates a change in the associated meansit controls. For example, the temperature signal from thermostat 98,which controls valve control means 46, shuts the steam valve at the settemperature so that the wet air mass is no longer heated. Likewise, thetemperature signal from thermostat 99, which controls baflle means 26,starts opening damper 24 and closing damper 22 at the set temperature sothat dry cold air from the outside is admitted into enclosure 12.

Since at the start of the degreening cycle the room is cold because thefruit is cold, and thermostat 98 is set to the desired fruit processingtemperature (72 F.), heat control means 46 maintains the steam valvefully open for maximum heating. At the same time thermostat 99, which isset to the desired dew point temperature (69? F.), maintains controlmeans 26 in a position so that damper 22 is wide open. Pump 58 isstarted and air entering air-conditioning device 10 through input port16 is fully saturated to about 100 percent relative humidity. The wetair mass then passes through heating element 42 Where it is warmed up(which decreases the relative humidity) and is expelled through outputport 20 in the partitioned portion. Fans circulate the air through theprocessing room and back to input port 16.

As a natural consequence of locating the spray water reservoir insideand on the bottom of enclosure 12, the spray water is constantly exposedto the upwardly moving air stream of the return air entering enclosure12 through input port 16. This return air stream heats the spray waterto and thereafter maintains the spray water at a temperature which isvery close to the dry bulb temperature.

The reason that the spray water temperature is not exactly equal to thedry bulb temperature of the return air stream is due to some evaporationfrom the surface of the spray Water reservoir which produces somecooling. Generally speaking, the smaller the evaporation from thereservoir the closer will the spray water temperature be to the dry bulbtemperature of the return air stream. Since the rate of evaporationdepends on the spread between the dry bulb temperature and the wet bulbtemperature of the air immediately in contact with the spray waterreservoir surface, and since this air has a relative humidity which issubstantially equal to 100% due to the spray water from spray tree 52,the dry bulb-wet bulb spread is always very small and the evaporation isnegligible. For all practical purposes, therefore, the spray water isheated to and thereafter maintained at the dry bulb temperature of thereturn air stream.

Maintaining the spray water at the return air temperature isparticularly important during the period of time during which theprocessing room is brought up to the processing temperature. Only afterthe processing temperature has been reached is input port 18 slightlyopened to admit a small amount of cold dry air to maintain the airstream temperature slightly below the dry bulb temperature of theprocessed fruit. However, the effect on the spray water temperature ofthe small amount of air entering through input port 18 is negligible andthe spray water remains substantially at the return air temperature.Further, the excess water from spray tree 50, and the water expelled byeliminator 64, likewise is exposed to the upward moving air stream ofthe return air within enclosure 12 and is heated thereby to the dry bulbtemperature of the return air. It is, of course, true that the upwardlymoving air stream is cooled during the adiabatic saturation process, butthis cooling produces only a temperature drop of a few degrees becausethe air stream has a high relative humidity at the temperature at whichit is returned to enclosure 12. Therefore this cooling efiect on theexcess and expelled water is likewise negligible.

Finally, enclosure 12 itself, together with the entire pumping system,is located in space 88 which likewise includes an upwardly moving airstream of return air which has, of course, the same dry bulb (and wetbulb) temperature as the air stream in enclosure 12 which is a partthereof. For this reason, the portion of enclosure 12 below heater 42,and the entire pumping system, is maintained at the return airtemperature which in turn assists in maintaining the temperature of thespray water substantially at the dry bulb temperature of the return air.Since the dry bulb temperature of the return air is substantially equalto the temperature of the fruit stored in the processing room, the spraywater temperature is maintained at and follows the fruit temperature.

Since heating element 42 constantly adds heat to the moving air mass,the air temperature and therefore the temperature of the fruit slowlyincreases while water vapor is constantly added. As the temperature ofthe stored fruit in room 80 approaches the desired temperature of say 72F. this fact is sensed by thermometer 96 and thermostat 98 puts out atemperature signal which shuts off heating means 42. As a consequence ofshutting off heating means 42 the temperature of the air passing throughenclosure 12 is not heated so that the air mass leaving output port 20now has a relative humidity of close to 100 percent.

However, before this condition is reached, the dew point temperature ofthe air mass will be above the dew point temperature set into thermostat99 which therefore provides a temperature signal on lead 101 whichactivates damper control means 26 to admit cold air from the outside.This cold air, of course, is dry and after being fully saturatedadiabatically is still colder than the temperature to which thethermostats are set. Accordingly, the colder saturated air will causeboth thermostats to provide temperature signals to admit air from theprocessing room and to require heating. Balance is achieved when justsufiicient cold and dry air from the outside is mixed with hot and Wetair from the processing room so that the temperature of the air mass ismaintained around the dew point temperature and the heating means raisesthe wet air mass moving therethrough the necessary amount to maintainthe processing room at the desired processing temperature.

It is also to be noted that during the period of time necessary to bringthe fruit in the processing room to the desired processing temperature,which typically takes 12 to 18 hours, water is constantly added so thatthe absolute humidity increases continually. During this time, therelative humidity may be maintained at a value which corresponds to thedifference between the returning air mass temperature and a dew pointtemperature a set number of degrees below by utilizing the control means102 shown in FIG. 6.

After the stored fruit has reached the desired processing temperature,it is typically maintained at the processing temperature for a period of24 to 72 hours.

There has been described an air-conditioning device which performs theprocess of raising the temperature of cold green fruit to a selectedprocessing temperature and thereafter for ripening of the fruit. Theprocess provides for increasing the absolute humidity of the air usedfor bringing the temperature of the fruit to the processing temperatureand, thereafter, for maintaining the air at a selected relativehumidity. Further, the process cools the fruit temperature, afterripening, by decreasing the absolute humidity of the air used to coolthe fruit.

What is claimed is:

1. The method of degreening and ripening fruit after picking, comprisingthe steps of:

storing the picked fruit, which is at a first temperature below aselected processing temperature, in an enclosed space;

forming an air stream having a dew point temperature which is maintainedas closely as possible to the temperature of the coldest portion of thefruit until reaching a selected dew point temperature and whichthereafter is maintained at the selected dew point temperature, and adry bulb temperature which is maintained at the selected processingtemperature; and

expelling said air stream into the enclosed space for circulationthrough the stored fruit until the fruit is degreened and ripened.

2. The method of degreening and ripening fruit after picking with an airstream which first raises and there after maintains the temperature ofthe fruit at a selected processing temperature, said method comprisingthe steps of:

storing the picked fruit, which is at a first temperature below saidselected processing temperature, in an enclosed space;

forming an air stream outside the enclosed space and circulating the airstream into and expelling the air stream out of the enclosed space andthrough the stored fruit;

saturating the air stream outside the enclosed space to a dew pointtemperature which is very close to the dry bulb temperature of the airstream expelled from the enclosed space;

heating the saturated air stream outside the enclosed space until thedry bulb temperature of the air stream expelled from the enclosed spacereaches the selected processing temperature; and

continuing the circulation process until the fruit is degreened andripened.

3. The method of degreening and ripening fruit of claim 2 which furtherincludes the step of maintaining the dew point temperature of thesaturated air stream at a selected maximum dew point temperature bymixing the saturated air with air from the outside atmosphere wheneverthe saturated air stream temperature dew point temperature exceeds saidselected dew point temperature whereby the air stream is maintained at aconstant relative humidity after the fruit temperature reaches theselected processing temperature.

4. The method of degreening and ripening fruit after picking, comprisingthe following steps of:

(a) storing the picked fruit, which is at a first temperature below aselected processing temperature, in an enclosed space;

(b) forming a first air stream from the air in the enclosed space andexpelling said first air stream into the enclosed space to cause aircirculation through the stored fruit;

(c) forming a second air stream from a selected portion of said firstair stream and a selected portion of the outside atmosphere andexpelling said second air stream into the enclosed space;

((1) adiabatically saturating said second air stream with watermaintained at a temperature substantially equal to the temperature ofsaid second air stream prior to saturation to produce a saturated airstream whose relative humidity is substantially equal to 100 percent;

(e) heating the saturated air stream until its dry bulb temperaturereaches said selected processing temperature;

(f) selecting the portions of air forming said second air stream so thatthe temperature of said saturated air stream, prior to being heated,does not exceed a selected dew point temperature; and

(g) continuously following steps (b), (c), (d), (e)

and (f) until the fruit is degreened and ripened.

References Cited UNITED STATES PATENTS 11/1931 Walsh 99-1O 3 5/1937Polderman 99103

